DESCRIPTION: This investigation will determine if the long term (8 weeks) administration of Hypericum perforatum to rats regulates ARTs similarly to, or differently from, long-term administration of prototypic antidepressant drugs. Additional data to be gained include the nature of any changes in ARTs during the course of Hypericum perforatum and whether this long-term administration regulates expression of genes thought to be activated during major depressive disorder (MDD). This study will offer information to be utilized to provide guidance in terms of dose and mechanism of action for subsequent phase I/II studies.